JPS6018196B2 - Electric motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a motor control device, and particularly to a motor control device using a thyristor chopper.

Recently, in order to control the power supplied to the motor, chopper circuits using thyristors etc. are used to control the voltage applied to the motor intermittently at a predetermined period, and to control the average value to the desired value. Similar methods have been proposed. In order to control the power supplied to the motor over a wide range, the chopper's conduction rate (the ratio of the on-time finger m to the chopper's on-off period T, T, /T, hereinafter referred to as conduction rate y) is used. It is also desirable to be able to control this over a wide range.
Therefore, a motor control device using a chopper circuit as shown in FIG. 1, for example, is known as a slave.

In Figure 1, Vs is a DC power supply, M is a motor armature,
F is a motor field, MSL is a smoothing reactor, CH is a magnet, and DF is a freewheel diode. These components constitute a known chopper-based motor control device. Further, the chopper CH is also known, and mainly includes a main thyristor MTh through which the motor current IM flows, a commutation thyristor Am that operates a commutation pulse current circuit for commutating the main thyristor Mm, and a whisker current voltage Vco. Commutation capacitor C for storage. , a commutating IJ factor L cooperating with the commutating capacitor Co to generate a commutating pulse current io. , a diode Dc that prevents the commutation exposure voltage Vco of the commutation capacitor Co from discharging when the main thyristor MTh is turned on. The gate of the main thyristor MTh of the Chotsupa is the output of the phase shifter APS, which is differentiated by a differentiating circuit DI, and the gate of the commutating thyristor ATh is the output of the oscillator OSC, which also serves as the power supply for the phase shifter A, is used by the differentiating circuit. The output width of the phase shifter, that is, the on-ratio of the main thyristor MTh (the on-ratio of the main thyristor MTh) is conduction rate) will be controlled. Figure 2 shows
This shows the operating waveforms of one cycle of chopper control in the circuit in Figure 1 described above.If we pay attention to the commutation operation period of the chopper CH, the current of the chopper CH actually becomes zero after the commutation thyristor ATh is turned on. It can be seen that the commutation operation time To is required before the switch is turned off.

This commutation operation time T. is commutated pulse current i. commutation half cycle ↑c (=m no Lo・Co), the time it takes for the reversal current of the commutation pulse current io to cancel the motor current IM flowing in the main thyristor Mm, 7M, the commutation capacitor Co
and a time 7c for charging the commutation voltage Vco. To widen the flow rate control range of chopper CH, use chopper C.
It is desirable to set the minimum conduction rate ymin of H to a value as small as possible.

The minimum conduction rate ymln of Chotsupa CH is the main thyristor M
When Th and commutating thyristor ATh are turned on at the same time, the value is tsumin=L'1)min-T.

[1}Denoted by T −T.

From this, it can be seen that in order to reduce the minimum conduction rate ymin of the chopper CH, it is necessary to reduce the commutation operation time To when the on-off period T of the chopper CH is constant. The voltage charging time 7c to the commutation capacitor Co is almost uniquely determined by the motor current IM at that time, so the commutation operation time T. To reduce commutation half cycle 7P
It is necessary to reduce 4. The commutation half-period 7P depends on the turn-off time of the thyristor used, but if the turn-off time is constant, decreasing the commutation half-period P will inevitably reduce the commutation pulse current i. . This will increase the wave height value. Now, in order to control the electric power coupled to the electric motor over a wide range, it is necessary to make the minimum flow rate ym1n of the chopper CH as small as possible. Increase the peak value of the pulse current io (for example, increase the peak value of the commutated pulse current io
3 to 5 times the motor current IM to be extinguished) to reduce the minimum conduction rate ymin.

For this reason, the current capacity of the commutating thyristor ATh increases, and the current capacity of the commutating capacitor C increases. The commutation device of the Chotupa CH has become large and expensive because the commutation capacitor capacity becomes large because the utilization rate of the commutation dew is poor. In addition, the motor current IM of the motor fluctuates depending on the size of the load connected to it, but since the commutation circuit constant is set so as to extinguish the maximum current as a chopper CH, the commutation pulse The current io is set to a large value regardless of the magnitude of the motor current IM, and the design of the commutation circuit is extremely uneconomical, which also makes the commutation circuit elements large and expensive. This is the cause of this. An object of the present invention is to provide a motor control device that eliminates the drawbacks of the prior art, reduces the pulse current withstand capacity of equipment in the commutation energy reversal path, and makes the commutation device small and inexpensive. It's about getting.

A feature of the present invention is that a saturable reactor type current transformer is provided to connect the commutation energy reversal path of the chopper and the motor current path.

FIG. 3 shows an embodiment of the present invention.

This embodiment differs from the conventional device shown in FIG. 1 in the primary winding N, which serves as a chopper commutation reactor, through which the chopper current icH flows, and in the commutation pulse current i. A saturable reactor type current transformer SCT having a secondary winding N2 through which current flows is provided,
Furthermore, in order to perform thinning control in a state of minimum conduction rate, the output of the phase shifter A tower is differentiated by a differentiating circuit D2 and is applied to the gate of the commutating thyristor ATh of the chopper. Note that the thinning control is provided as necessary, as will be described later. First, convert the commutation reactor into a saturable reactor type current transformer S.
The effects of using CT will be described.

FIG. 4 shows the operating waveform of one cycle of chopper control in the circuit of FIG. 3. If we pay attention to r during the commutation energy inversion period of the chopper CH, the commutation pulse current io is i. = Mother - N (mother - iCH), and the current value always matches the motor current IM. This is because in FIG. 3, where the main thyristor MTh is turned on and the chopper current lcH (=1-) flows through the primary winding N of the converter SCT,
Since the commutating thyristor ATh is turned on, the commutating capacitor C is connected to its secondary winding N2 due to the current transforming action of the current transformer SCT.
. From my mother. - This is because a current of N will flow.
FIG. 5 shows the operating waveforms of the current transformer SCT during this commutation operation period. The chopper current lcH flowing through the primary winding N,
(=IM), the magnetic flux level of the current transformer SCT is at the positive saturation value ■F in the ■i curve (■: magnetic flux, i: excitation current) in FIG. 5C.

In this state, when the commutating thyristor ATh is turned on, the commutating capacitor voltage Vco is applied to the secondary winding N2 of the current transformer SCT.
is applied, and the magnetic flux level changes from the positive saturation value to the negative saturation value■
The current is pulled back toward n, and due to the current transformation effect at this time, the current of mother -.M flows in the secondary winding N2 as a commutated capacitor fake current.

Commutation capacitor voltage Vc. The current gradually decreases to zero due to the discharge current mother-M, but now the current flowing through the secondary winding N2 flows as a full current of the commutating capacitor Co, and the commutating capacitor voltage Voo will be charged with the opposite polarity from the previous polarity. As a result, the polarity of the voltage applied to the secondary winding N2 is also reversed, so that the magnetic flux level of the current transformer SCT is again pulled back to the positive saturation value ○P. When the magnetic flux level of the current transformer SCT reaches a positive saturation value, the saturation inductance of the secondary winding N2 decreases rapidly, and the main thyristor arc extinction period ↑N10c occurs. The commutating thyristor ATh and the main thyristor MTh are turned off by the L-C oscillating current caused by the inductance and commutating capacitor. After that, the chopper current lcH
(=IM) flows through the diode Dc → the secondary winding N2 → the commutating capacitor Co, and when the commutating capacitor voltage Vco is charged to a predetermined value, the electric current lcH becomes zero,
In other words, the Chotsupa CH is turned off. In this thyristor extinction period M+↑c, Co→MTh(
A current flows in the main thyristor arc-extinguishing path (reverse direction)→Dc→N2→Co, but in this embodiment, this current does not become larger than the current IM flowing in the forward direction of the main thyristor MTh. Therefore, as shown in FIG. 5, the voltage-time product of the saturable reactor type current transformer SCT is adjusted so that the time 7 during which current transformation is performed is equal to the commutation half period P of the conventional circuit of FIG. By determining , the minimum conduction rate min of the chopper CH can be made equal to that of the conventional circuit shown in FIG. Fifth
From the figure, the current transformation action time 7T can be considered to be approximately twice the time for the magnetic flux of the saturable reactor type current transformer SCT to change from the positive saturation value to the negative saturation value, so the saturable reactor type current transformer The voltage time value V・S of SCT is V・S=VC.

X Cow The time product V・S is V・S=2N2・B・A
...{31, so these '2} ~ '3
}The material and dimensions of the huanshin to be used can be determined from the formula.

By the way, in the circuit of the present invention shown in FIG. 3, the commutating capacitor Co
The charging and discharging current, that is, the commutation pulse current i.

As a result, if the commutating capacitor voltage Vco is assumed to be constant, the current commutation action time ↑ will vary depending on the magnitude of the motor current IM. There is a risk of change. Generally, the commutating capacitor voltage Vco is overcharged to more than the power supply voltage Vs due to the inductance L' of the circuit through which a large current flows to the commutating capacitor Co, that is, the inductance L' caused by the commutating reactor, wiring, etc. It is well known that the value is vC.

=vS+・M. shop . - Indicated by skin '4'.

From this, if the commutation circuit constant is set so that the overcharge voltage is larger than the power supply voltage VS within the control range of the motor current IM, the commutation capacitor voltage Vco will be approximately proportional to the motor current IN. Therefore, unlike the case where the commutating capacitor voltage Vco is constant, it does not vary significantly depending on the magnitude of the motor current IM. Therefore, the current transformation action time 7T of the above-mentioned saturable reactor type current transformer SCT may be determined so as to obtain the required minimum conductivity ymin at the minimum control current (IN)min of the motor current IN. Note that the primary winding N of the saturable reactor type current transformer SCT in the embodiment shown in FIG. It has the characteristic that the required commutation capacitor voltage can be obtained by appropriately selecting .

In the embodiment shown in FIG. 3 described above, it has been explained that the chopper current (=motor current) flows through the primary winding N of the saturable reactor type current transformer SCT.
．． The connection location is not limited to this, and other locations through which the motor current flows, such as the embodiments shown in FIGS. 6 to 8, are conceivable.

In FIG. 6, the primary winding N of a saturable reactor type current transformer SCT is connected in series with a motor. If the square characteristics of the iron core used in the saturable reactor type current transformer SCT are poor, the iron core magnetic flux of the saturable reactor type current transformer SCT will not be at the positive saturation value just before turning on the chopper CH. Since the iron D magnetic flux changes to a positive saturation value by turning on, almost the power supply voltage Vs is applied to the primary winding N of the saturable reactor type current transformer SCT during this time, and this voltage is applied to the saturable reactor type current transformer SCT. A voltage (band-VS) determined by the transformation ratio band is applied to the secondary winding N2 of the transformer SCT.

Therefore, in the case of the circuit shown in Fig. 3, the commutating thyristor ATh
and diode Dc, and each time the chopper CH turns on, the voltage of the secondary winding N2 (=
VS) will be applied,
This results in the disadvantage that a high voltage withstand capacity is required. The circuit in Figure 6 shows the primary winding N of the saturable reactor type current transformer SCT.
, is connected in series with the motor, and the motor current continues to flow through the primary winding N, even when the chopper CH is turned on, that is, even when the chopper CH is turned off, and the iron core magnetic flux of the saturable reactor type current transformer SCT is brought to almost positive saturation. By maintaining this value, the above-mentioned drawbacks are eliminated.

In addition, in this circuit of Fig. 6, the saturable reactor type current transformer S
CT primary winding N. Although there is a drawback that the saturated inductance of 2 cannot be used as the inductance that contributes to the overcharge voltage to the commutating capacitor, this can be sufficiently covered by methods such as increasing the length of the wiring from the power supply to the switch. In the embodiment shown in FIG. 7, one of the saturable reactor type current transformers SCT is installed at a location that takes advantage of the features of FIGS. 3 and 6, respectively.
The secondary winding N, is connected to the primary winding N, with suitable taps, one part of which is in series with the motor, and the other part in series with the chopper. In addition, in the embodiment of FIG. 8, similar to the circuit of FIG. 7, an appropriate tap is provided on the primary winding N, and one part of the tap is connected in series with the freewheel diode DF through which the motor current flows when the chopper is turned off. The part is arranged in series with the chopper. Therefore, in the embodiments shown in FIGS. 7 and 8, the primary winding N of the saturable reactor type current transformer SCT can be used as an inductance that contributes to the overcharge voltage to the commutating capacitor, and also as a chopper. A feature is that unnecessary voltage is not applied to the commutating thyristor and diode when turned on. Therefore, according to the circuit of FIG. 3, by providing a saturable reactor type current transformer SCT as a commutating reactor, the commutating pulse current i can be reduced.

Always set the value commensurate with the motor current IM. =IM), this has the effect of reducing the current capacity of the commutating thyristor ATh and the commutating capacitor capacity. In addition, saturable reactor type current transformer SCT
The current transformation action time 7T is the required chopper minimum flow rate ymi
By setting so that n can be obtained, it is possible to control the electric motor over a wide range similar to that of the slave device. The embodiments described above can be applied to applications where the load is heavy and the minimum control value of the motor current is relatively large, such as the motor control of an electric car, and in this case, the chopper CH
The oscillation path output may be applied to the gate of the commutating thyristor ATh as in the conventional circuit.

Next, in the circuit shown in Fig. 3, the chopper CH is thinned out in a state of minimum conduction rate, that is, the effect of differentiating the fall of the phase shifter output to the gate of the chopper/be day commutation thyristor ATh. Let's talk about.

For example, when extremely slow and slow operation is required, such as when controlling a motor for a forklift, the minimum control value (IM) min of the electric motor 11 is also required to be a very small value. The commutating capacitor voltage Vc when
o is charged to a constant value of the power supply voltage Vs with almost no overcharging pressure. Therefore, even if an attempt is made to reduce the motor current IN, the current transformation operation time 7T of the saturable reactor type current transformer SCT, that is, the commutation operation time To becomes large, and the required minimum value control cannot be performed. In the circuit shown in Figure 3, Chotsupa C
The condition that the main thyristor MTh turns on the gate pulse of the commutating thyristor ATh of H, that is, the commutating thyristor AT
The gate pulse h is given by differentiating the falling edge of the phase shifter output that changes the on-ratio of the main thyristor MTh. An operating waveform diagram in this case is shown in FIG. Note that the maximum flow rate ymin of the chopper CH is set to a value that allows minimum value control required in normal operation control. The phase shifter is
The output width of the motor current IM is controlled by the output from the current control system so that it follows the current command IP, but if the minimum distant current rate ymin of Choch °C day is large, the motor current ln is higher than the current command IP. If it is large, the phase shifter output width becomes zero, and both the main thyristor MTh and the commutating thyristor Am are not turned on. In this state, motor current IM
decreases, and when it becomes smaller than the current command IP, a transfer device output is generated and the main thyristor MTh and commutating thyristor ATh
are both turned on, and the motor current IM also becomes larger than the current command IP. Thereafter, this operation is repeated, and the motor current IM is maintained approximately at the current command IP. In other words, the chopper CH has approximately the minimum conductivity ym as shown in FIG.
The state of "in" is thinned out and controlled, and the conduction rate at a temperature of 100° C. can be equivalently controlled to a value smaller than the minimum conduction rate ymin. Therefore, according to the circuit shown in FIG. 3, the commutating thyristor current capacity and commutating capacitor capacity can be reduced compared to the conventional device, and the chopper conduction rate can be equivalently and continuously controlled to almost zero, so that the above-mentioned slow speed operation can be achieved. This has the effect of enabling suitable minimum current control. As explained above in detail, according to the circuit shown in FIG. 3, a saturable reactor type current transformer is used as a commutating IJ vector to always perform a commutating operation commensurate with the motor current. This has the effect of reducing current capacity and commutation capacitor capacity.

Further, according to the circuit shown in FIG. 3 of the present invention, the motor current can be controlled over a wide range by controlling the chopper to thin out the paddy state with the minimum conductivity. To show experimental values regarding the effects of the present invention, in a forklift motor control device for a forklift with a power supply voltage Vs = 36V and a motor current control range of 5M to 60 ships, the conventional circuit shown in Fig. 1 has a commutation capacitor capacity of 40V.
The circuit of the present invention (the saturable reactor type current transformer is made of silicon steel plate, A = 6 × 10-6〆, N, = 3T, N2 = 51) According to the results, the commutating capacitor capacity was 200 F, and the commutating thyristor current capacity was approximately half that of the LO ship.

In addition, in the experiment, in the circuit of the present invention, the commutation inversion current that cancels out the motor current flowing through the main thyristor is controlled only by the saturation inductance of the saturable reactor type current transformer, resulting in a steep current, so that the main thyristor current is canceled out. The time ↑w required for the saturable reactor type current transformer to return from around the negative saturation value to the positive saturation value is smaller than that of the conventional circuit, and the commutating capacitor voltage decreases to the primary winding element. is induced by the voltage ratio between the motherboard and the VCO, and this value becomes larger than the power supply voltage Vs due to the overcharge voltage of the commutation capacitor, so the main thyristor current that should actually be extinguished decreases, making commutation easier. It was found that this has a positive effect. Of course, these effects are of no small help in reducing the capacitance of the commutation capacitor by half. Note that the present invention is not limited to the above-described embodiments, and may be applied to, for example, a chopper circuit in which a well-known commutating thyristor and a commutating L-C circuit are connected in series, and a phase shifter output as a chopper gate control circuit. The commutating thyristor is turned on at the rising edge of the phase shifter (in this case, the main thyristor is turned on at the falling edge of the phase shifter output), and the current control system includes a control stabilizing element (generally This can be applied to devices with a first-order delay element).

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional device, FIG. 2 is an explanatory diagram of the operation of the conventional circuit shown in FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment of the present invention.
4 and 5 are explanatory diagrams of the operation of the circuit according to the embodiment of the invention shown in FIG. 3, FIGS. 6 to 8 are circuit diagrams showing other embodiments of the invention, and FIG. It is an explanatory diagram. M...Motor armature, F...Motor field, MSL...
...Smooth reactor, DF...Freewheel
diode, CH... Chotsupa, MTh...
...Main thyristor, ATh...Commuting thyristor, Co...Commuting capacitor, L. ...Commutation reactor, SCT...Saturable reactor type current transformer, N. ...Primary winding of SCT, N2...Secondary winding of SCT. Younger brother' figure 2
Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Mine? figure

Claims (1)

[Claims] 1 A DC power source, a motor supplied with power from the DC power source, a chopper device connected between the DC power source and the motor, and a duty ratio control device for the chopper device, the chopper device mainly controlling the motor current. It consists of a main thyristor for commutating current, a commutation thyristor for commutating the main thyristor, a capacitor for storing commutation energy, and a means for reversing the commutation energy, and the commutation energy is reversed as a current path through the commutation capacitor. a first winding connected in the motor current path;
A saturable reactor type current transformer comprising a second winding connected to the commutation energy reversal path and having a current transformer action between the motor current and the commutation energy reversal current. Electric motor control device.